Study On Volatile Flavor Compounds Of Low-sodium Ham And Their Interaction With Myosin At Different Temperatures

Dry-cured ham,a traditional cured meat product,is favored by consumers in China.However,the high sodium content in ham is not conducive to human health.And the processing cycle of ham is long,which consumes a lot of manpower and material resources and increases the cost of the enterprise.Reducing the sodium salt content and shortening the processing time have become an important goal of the food industry.Currently,a common way to reduce the sodium salt content of dry-cured ham is to partially replace the sodium salt with a chloride salt.Flavor is an important quality indicator for dry-cured ham,an important factor in determining the level of dry-cured ham and attracting consumers to purchase.The flavor compounds can be bound to the muscle protein in the food by molecular bonds.The interaction of the muscle protein and volatile flavor compounds affects the release of flavor compounds,thereby affecting the final food flavor quality.Myofibrillar protein is a major component of muscle protein.Myosin is the most important part of myofibrillar proteins,which may play a critical role in binding and releasing volatile compounds in meat products,in particular to dry-cured ham.The interaction of proteins and volatile flavors depends not only on the type of flavor compounds and the nature of the protein itself,but also on other media conditions,such as temperature.At present,the interaction mechanism between myosin and volatile flavor substances is not yet understood.Therefore,this thesis will use KCl partial replacement of Na Cl mixed low sodium salt as a salting preparation,combined with enhanced high temperature maturation process to make ham,in order to reduce the sodium content in the ham and shorten the processing cycle,explore the volatile flavor compounds of low-sodium ham at different processing stages,and find the main influencing factors of its unique flavor,and bind with myosin at different temperatures,exploring mechanism of interaction of myosin and volatile flavor compounds,which provides a theoretical basis for improving the flavor quality of products.The main results are as follows:1.Study on volatile flavor compounds of low-sodium dry-cured ham and principal component analysisIn this chapter,low-sodium dry-ham ham was made by intensifying high-temperature ripening with 30 % KCl and 70 % Na Cl as the curing agent.The volatile flavor compounds of low-sodium ham in different processing stages were determined,and the changes of flavor compounds during ham processing were revealed.Principal component analysis method was used to find the volatile flavor compounds which mainly contribute to ham flavor,providing flavor selection basis for the study of the interaction between myosin and volatile flavor compounds.The results showed that 59 volatile flavor compounds were identified during the processing of low-sodium dry-cured ham,including 9 aldehydes,7ketones,6 esters,6 acids,8 alcohols and 11 alkanes.The hams at different processing stages had unique volatile flavor compounds.The main volatile flavor compounds in the green ham stage were pentadecane and tetradecane;the main volatile flavor compounds in the low temperature fermentation stage were ethyl octanoate and undecanal;the main volatile flavor compounds in the medium temperature fermentation stage were3-methyl-1-butanol,butyric acid,cyclododecanone,ethyl decanoate,2-decyne and2-heptanone;the main volatile flavor compounds in the high temperature fermentation stage were 3-methylbutanal,dimethylpyrazine,2-hexadecanol,pentamethylheptane,phenylacetaldehyde,and octanal.And 3-methylbutanal,dimethylpyrazine,pentamethylheptane,octanal,2-hexadecanol,phenylacetaldehyde,3-methyl-1-butanol,butyric acid,2-heptanone,cyclododecanone,ethyl decanoate and 2-decyne were the main characteristic volatile flavor compounds of low-sodium dry-cured ham.2.Study on the binding of myosin and volatile flavors at different temperaturesThis chapter used spectroscopy to explore the binding of myosin and five volatile flavor compounds at 4,25,37 and 60 °C.The five volatile flavor compounds were hexanal,octanal,3-methylbutyraldehyde,2-heptanone and ethyl hexanoate,which were determined by the results of the first chapter.Fluorescence quenching method confirmed that the binding of myosin and volatile flavor compounds;UV-visible spectroscopy and Fourier transform infrared(FITR)spectroscopy not only explored the binding,but also the effects of flavor compounds on myosin conformation.The results showed that temperatures has an impact on the conformation of myosin.Added to myosin,the flavor compounds had strong quenching effects on the intrinsic fluorescence of myosin;the UV-vis and FITR of myosin were also changed,indicating that myosin interacts with flavor compounds.In addition,it was found that the conformation of the myosin was not only affected by temperature but also volatile flavor compounds.3.Study on the binding ability of myosin to volatile flavors at different temperaturesThis chapter explored the binding ability of myosin and five volatile flavor compounds at 4,25,37 and 60 °C.The binding thermodynamics of myosin and flavor compounds was investigated by isothermal titration calorimetry(ITC)technique at different temperatures.The binding constants and thermodynamic parameters were obtained,including enthalpy change,entropy change and Gibbs free energy,and the binding constants;surface plasmon resonance(SPR)technology explored the binding kinetics to obtain the dissociation constants at different temperatures;solid-phase microextraction combined with gas chromatography-mass spectrometry(SPME-GC-MS)was used to research the binding amounts of myosin and flavor compounds at different temperatures.The results show that interactions of myosin and aldehydes compounds were spontaneous and exothermic with rapid binding and rapid dissociation.Moreover,the molecular bonds of interactions were hydrogen bonds and van der Waals forces.The binding constants and dissociation constants of myosin and volatile flavor compounds were highest at 37 °C.Ethyl hexanoate was significantly higher than other flavor compounds(P<0.05).Linear aldehydes were also significantly higher than branched aldehydes(P<0.05);The binding amount of myosin and volatile flavor compounds at 37 °C was significantly more than at 4,25 and 60 °C(P<0.05).The binding amounts for aldehydes were significantly more than that for other flavor compounds(P<0.05).In addition,the binding amounts for linear aldehydes were significantly more than that for branched aldehydes(P<0.05).It can be seen that the greatest binding ability of myosin and volatile flavor compounds was at 37 °C,and the binding ability for linear aldehydes was greater than that for branched aldehydes.